How the Human Blockhead Works

Sneezing is partially reflexive. The nerve signalsthat control sneezing travel along a reflex arc.

When you watch someone perform the human blockhead trick, you probably wonder if he is in any pain. After all, a nail is sharp, and the inside of the nose is sensitive. Putting a foreign object deep into your nasal cavity isn't particularly comfortable, and it can be certainly painful when the performer is learning to do the trick. However, another obstacle -- sneezing -- can be harder to overcome.

Sneezing is a largely reflexive act that usually occurs when something irritates your nasal passageways. As with all reflexes, sneezing involves a reflex arc consisting of a receptor, a sensory nerve, an integration center, a motor nerve and an effector. Here's what happens:

The receptors, which are nerve endings in your nasal passageways, detect an irritant. This irritant might be an unusual smell, dust, animal dander, pepper, viruses that attack the mucous membranes or a variety of other substances.

Nerves carry these impulses to the sneezing center in your brain stem.

The sneezing center sends its instructions along your facial nerve and the nerves that lead to your lungs and diaphragm.

Your eyes start to water, and your nasal passageways secrete fluid. Your diaphragm moves abruptly, causing you to take a deep breath. Then, it and the muscles in your chest contract, causing the air to leave your nose and mouth suddenly and rapidly.

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The sneeze reflex must be contained if the human blockhead trick is to be successful.

Photo courtesy of Thom Sellectomy

It's possible to put off sneezing, ignoring the tickling sensation in your nose. If the sensation passes, you can get away without sneezing. This isn't always possible, though -- sometimes, you simply have to sneeze.

On top of ruining the effect, sneezing while attempting to put a nail into the nasal cavity could be very dangerous. The sharp intake of air before the sneeze could potentially pull the foreign object further into the nasal passageway than the performer intends. The sudden movement of the head could also cause sharp objects to scrape against the interior of the passage. So when learning to perform the human blockhead act, people have to learn to ignore their sneeze reflex. Much like in sword swallowing, this can take a lot of practice.

The sneeze reflex is one of your body's defense mechanisms against bacteria and viruses-- when you sneeze, you forcibly expel particles that could make you sick. In other words, a human blockhead ignores one of the tools the body uses to prevent illness. In addition, the trick requires a person to place a foreign object in very close proximity to his sinuses and throat. This can potentially lead to illnesses, particularly sinus and throat infections. This is especially true when performers work in crowded conditions, like fairs and festivals. The foreign object is also a physical hazard, which has the potential to damage the tissues inside the nose and nasal cavity.

As with sword swallowing, performers who try the human blockhead put themselves at risk in pursuit of entertainment. It's not an activity that you should try at home or without the help of an experienced performer.

To learn more about the human blockhead and related acts, check out the links below.

Sneezing in the Sun

Some people sneeze when they look at bright light or when they walk from a relatively dark room into bright sunlight. This behavior is known as the photic sneeze reflex, and researchers aren't exactly sure what causes it.